/******************************************************
Executes SQL stored procedures and their control structures

(c) 1998 Innobase Oy

Created 1/20/1998 Heikki Tuuri
*******************************************************/

#include "eval0proc.h"

#ifdef UNIV_NONINL
#include "eval0proc.ic"
#endif

/**************************************************************************
Performs an execution step of an if-statement node. */

que_thr_t *if_step(
    /*====*/
    /* out: query thread to run next or NULL */
    que_thr_t *thr) /* in: query thread */
{
  if_node_t *node;
  elsif_node_t *elsif_node;

  ut_ad(thr);

  node = thr->run_node;
  ut_ad(que_node_get_type(node) == QUE_NODE_IF);

  if (thr->prev_node == que_node_get_parent(node))
  {
    /* Evaluate the condition */

    eval_exp(node->cond);

    if (eval_node_get_ibool_val(node->cond))
    {
      /* The condition evaluated to TRUE: start execution
      from the first statement in the statement list */

      thr->run_node = node->stat_list;
    }
    else if (node->else_part)
    {
      thr->run_node = node->else_part;
    }
    else if (node->elsif_list)
    {
      elsif_node = node->elsif_list;

      for (;;)
      {
        eval_exp(elsif_node->cond);

        if (eval_node_get_ibool_val(elsif_node->cond))
        {
          /* The condition evaluated to TRUE:
          start execution from the first
          statement in the statement list */

          thr->run_node = elsif_node->stat_list;

          break;
        }

        elsif_node = que_node_get_next(elsif_node);

        if (elsif_node == NULL)
        {
          thr->run_node = NULL;

          break;
        }
      }
    }
    else
    {
      thr->run_node = NULL;
    }
  }
  else
  {
    /* Move to the next statement */
    ut_ad(que_node_get_next(thr->prev_node) == NULL);

    thr->run_node = NULL;
  }

  if (thr->run_node == NULL)
  {
    thr->run_node = que_node_get_parent(node);
  }

  return (thr);
}

/**************************************************************************
Performs an execution step of a while-statement node. */

que_thr_t *while_step(
    /*=======*/
    /* out: query thread to run next or NULL */
    que_thr_t *thr) /* in: query thread */
{
  while_node_t *node;

  ut_ad(thr);

  node = thr->run_node;
  ut_ad(que_node_get_type(node) == QUE_NODE_WHILE);

  ut_ad((thr->prev_node == que_node_get_parent(node)) || (que_node_get_next(thr->prev_node) == NULL));

  /* Evaluate the condition */

  eval_exp(node->cond);

  if (eval_node_get_ibool_val(node->cond))
  {
    /* The condition evaluated to TRUE: start execution
    from the first statement in the statement list */

    thr->run_node = node->stat_list;
  }
  else
  {
    thr->run_node = que_node_get_parent(node);
  }

  return (thr);
}

/**************************************************************************
Performs an execution step of an assignment statement node. */

que_thr_t *assign_step(
    /*========*/
    /* out: query thread to run next or NULL */
    que_thr_t *thr) /* in: query thread */
{
  assign_node_t *node;

  ut_ad(thr);

  node = thr->run_node;
  ut_ad(que_node_get_type(node) == QUE_NODE_ASSIGNMENT);

  /* Evaluate the value to assign */

  eval_exp(node->val);

  eval_node_copy_val(node->var->alias, node->val);

  thr->run_node = que_node_get_parent(node);

  return (thr);
}

/**************************************************************************
Performs an execution step of a for-loop node. */

que_thr_t *for_step(
    /*=====*/
    /* out: query thread to run next or NULL */
    que_thr_t *thr) /* in: query thread */
{
  for_node_t *node;
  que_node_t *parent;
  lint loop_var_value;

  ut_ad(thr);

  node = thr->run_node;

  ut_ad(que_node_get_type(node) == QUE_NODE_FOR);

  parent = que_node_get_parent(node);

  if (thr->prev_node != parent)
  {
    /* Move to the next statement */
    thr->run_node = que_node_get_next(thr->prev_node);

    if (thr->run_node != NULL)
    {
      return (thr);
    }

    /* Increment the value of loop_var */

    loop_var_value = 1 + eval_node_get_int_val(node->loop_var);
  }
  else
  {
    /* Initialize the loop */

    eval_exp(node->loop_start_limit);
    eval_exp(node->loop_end_limit);

    loop_var_value = eval_node_get_int_val(node->loop_start_limit);

    node->loop_end_value = eval_node_get_int_val(node->loop_end_limit);
  }

  /* Check if we should do another loop */

  if (loop_var_value > node->loop_end_value)
  {
    /* Enough loops done */

    thr->run_node = parent;
  }
  else
  {
    eval_node_set_int_val(node->loop_var, loop_var_value);

    thr->run_node = node->stat_list;
  }

  return (thr);
}

/**************************************************************************
Performs an execution step of a return-statement node. */

que_thr_t *return_step(
    /*========*/
    /* out: query thread to run next or NULL */
    que_thr_t *thr) /* in: query thread */
{
  return_node_t *node;
  que_node_t *parent;

  ut_ad(thr);

  node = thr->run_node;

  ut_ad(que_node_get_type(node) == QUE_NODE_RETURN);

  parent = node;

  while (que_node_get_type(parent) != QUE_NODE_PROC)
  {
    parent = que_node_get_parent(parent);
  }

  ut_a(parent);

  thr->run_node = que_node_get_parent(parent);

  return (thr);
}
